Lundegard’s theory: Lundegard’s theory is also called the cytochrome pump theory. According to this theory cytochrome is the career. According to this theory ion absorption, in fact, takes place through the cytochrome system. Lundegard opined that proton (H+) and electron (e–) are formed in the inner space due to the reaction of dehydrogenize. The electron comes out through the cytochrome chains and forms water with the combination of oxygen and proton (H+). As a result, the reduced ion becomes oxidized by losing an electron (e–) and receives an anion (A–)

The oxidized iron of cytochrome of the inner space is reduced by receiving an electron (e–) from the dehydrogenase reaction and in the outer space the oxidized iron eventually releases the anion at the end of the reaction to the inner space which it receives.

By this way anions (A–) are stored in the inner space. Due to the strong anions in the inner space a difference of ion nature, example, electric charge is made between the outer space and the inner space. Donan equilibrium formed which results in the passive absorption of cations.